The present invention relates to motion control systems and, more specifically, to diagnosing failure conditions in a linear drive system in a motion control system, where the motion control system incorporates multiple movers propelled along a track using the linear drive system.
Motion control systems utilizing movers and linear motors can be used in a wide variety of processes (e.g. packaging, manufacturing, and machining) and can provide an advantage over conventional conveyor belt systems with enhanced flexibility, extremely high-speed movement, and mechanical simplicity. The motion control system includes a set of independently controlled “movers” each supported on a track for motion along the track. The track is made up of a number of track segments that, in turn, hold individually controllable electric coils. Successive activation of the coils establishes a moving electromagnetic field that interacts with the movers and causes the mover to travel along the track. Sensors may be spaced at fixed positions along the track and/or on the movers to provide information about the position and speed of the movers.
Each of the movers may be independently moved and positioned along the track in response to the moving electromagnetic field generated by the coils. In a typical system, the track forms a closed path over which each mover repeatedly travels. At certain positions along the track other actuators may interact with each mover. For example, the mover may be stopped at a loading station at which a first actuator places a product on the mover. The mover may then be moved along a process segment of the track where various other actuators may fill, machine, position, or otherwise interact with the product on the mover. The mover may be programmed to stop at various locations or to move at a controlled speed past each of the other actuators. After the various processes are performed, the mover may pass or stop at an unloading station at which the product is removed from the mover. The mover then completes a cycle along the closed path by returning to the loading station to receive another unit of the product.
A linear drive system presents challenges for detecting component failures that are not seen in rotary motors or rotary drive systems. Whereas failure of a coil in a stator of a rotary machine is readily observed due to repeated activation and subsequent degradation in performance, failure of a coil in a linear drive system may not be readily observed. A linear drive system includes a number of coils spaced along a track. The coils are activated to cause a mover to travel along the track. Each coil is activated only when a mover passes over the coil. The momentum of the mover allows the mover to continue traveling across any one coil that may fail, and adjacent coils to a failed coil may compensate, at least in part, for a failed coil. However, extra current applied to adjacent coils to compensate for a first, failed coil may result in accelerated failure of those coils.
Similarly, failure of a position sensor in a rotary machine would be readily observed, again due to repeated activation of the sensor as the machine rotates. However, a linear drive system may employ one or more position magnets on each mover and an array of position sensors spaced along the track to detect the position magnets on each mover as it passes. Failure of a single position sensor may go undetected as adjacent position sensors are able to compensate and provide position information for each mover.
Thus, it would be desirable to provide a method and system for detecting and reporting component failures in a linear drive system.